A nanocomposite adsorbent for oil shale slag, its preparation method and application

Abstract

This invention relates to the field of inorganic non-metallic adsorbent technology, specifically an oil shale slag nanocomposite adsorbent, its preparation method, and its application. It addresses the problems of low controllability, poor stability, poor adsorption effect, poor repeatability, and short cycle life associated with the application of oil shale slag as an adsorbent. The invention involves dispersing oil shale slag powder in a sodium silicate nonahydrate aqueous solution, stirring, and ultrasonicating to obtain suspension 1. A manganese sulfate aqueous solution is added to suspension 1 to obtain suspension 2. Suspension 2 undergoes a hydrothermal reaction, and the reaction product is centrifuged until the pH is neutral. The product is then dried, ground, and sieved to obtain the oil shale slag nanocomposite adsorbent, which can be applied to the adsorption of organic dyes. This invention significantly improves the reactivity, removal capacity, and adsorption stability of the oil shale slag nanocomposite adsorbent for organic pollutants, exhibiting excellent repeatability and cycle life, providing an economical, environmentally friendly, and sustainable solution for water treatment and solid waste management.

Description

Technical Field

[0001] This invention relates to the field of inorganic non-metallic adsorbent technology, specifically to an oil shale slag nanocomposite adsorbent, its preparation method, and its application. Background Technology

[0002] The large amount of oil shale residue produced after oil shale incineration is rich in silicates, calcium oxide, and various metal oxides, and is considered a solid waste resource with potential adsorption activity. Researchers have attempted to utilize its alkaline mineral components, silica-alumina framework, and surface functional groups to fix or remove organic dyes. However, as related research has progressed, the low controllability and poor stability of oil shale residue in aquatic environments have severely limited its adsorption effect, and significantly weakened its environmental friendliness and engineering controllability as a solid waste resource recovery material.

[0003] Oil shale slag (OSC) has a high content of free calcium oxide, which readily hydrates into calcium hydroxide upon entering water. This keeps the leachate discharged or seeping into the soil highly alkaline for decades, posing a risk of secondary pollution to surrounding water bodies and soil. This continuous and uncontrollable release of alkalinity can cause the dissociation, aggregation, or transformation of dye structures, severely affecting dye removal efficiency and hindering the long-term stable operation of the engineering system. Furthermore, the dense pore structure and low specific surface area of ​​oil shale slag limit the number of effective adsorption sites, making its adsorption process heavily reliant on surface precipitation and ion exchange mechanisms. This results in low adsorption capacity, slow adsorption rate, and long equilibrium time. Under prolonged contact with water, carbonate inorganic salt deposition can easily occur within the pores, leading to pore blockage, bed hardening, and decreased adsorption performance.

[0004] Furthermore, the chemical composition and mineral phases of oil shale slag are significantly affected by the mineral source, process, and incineration conditions. Fluctuations in the proportions of free CaO, sulfate, aluminosilicate, and trace metals between different batches can cause differences in surface charge, hydrophilicity / hydrophobicity, and alkalinity release rates. This makes it difficult to reproduce the adsorption capacity, adsorption kinetics, and equilibrium pH performance for cationic or anionic dyes, resulting in inconsistent quality of oil shale slag adsorbents during application. Moreover, in complex wastewater systems, coexisting ions (such as Na+) can cause problems. + Ca 2+ SO4 2- CO3 2-Furthermore, through charge shielding, ion competition, or complexation, the adsorption performance under actual operating conditions differs significantly from the ideal state, making it difficult to meet the stability and predictability requirements of engineering treatment. Since the adsorption of oil shale slag mainly relies on weak physical interactions and surface deposition, the material's structural stability is limited. During conventional acid washing and alkali washing regeneration operations, problems such as adsorption capacity decay, reduced particle strength, and increased pulverization easily occur. If an enhanced chemical regeneration system is used, it may cause irreversible changes in the mineral structure or damage to surface functional groups, significantly shortening the material's service life and increasing treatment costs, thus greatly limiting the cycle life and economic viability of oil shale slag adsorbents.

[0005] Therefore, in order to improve the above-mentioned defects, it is necessary to develop a new type of composite adsorbent material that can effectively improve the utilization efficiency of oil shale slag, mitigate environmental risks, and realize the resource utilization of solid waste. This has significant engineering, environmental, and application prospects for promoting the recycling of solid waste resources and improving the quality of the ecological environment. Summary of the Invention

[0006] To address the problems of low controllability, poor stability, poor adsorption effect, poor repeatability, and short cycle life in the application of oil shale slag as an adsorbent, this invention proposes an oil shale slag nanocomposite adsorbent, its preparation method, and its application. The technical solution of this invention is as follows:

[0007] A method for preparing an oil shale slag nanocomposite adsorbent includes the following preparation steps: dispersing oil shale slag powder in an aqueous sodium silicate nonahydrate solution, stirring and sonicating to obtain suspension 1; adding an aqueous manganese sulfate solution to suspension 1 to obtain suspension 2; subjecting suspension 2 to a hydrothermal reaction, centrifuging the reaction product until the pH is neutral; drying, grinding, and sieving to obtain the oil shale slag nanocomposite adsorbent.

[0008] Furthermore, the oil shale residue powder is prepared by mixing oil shale residue at 200 r·min -1 The oil shale slag powder was obtained by ball milling at a certain speed for 40 minutes; the particle size of the powder was 0.075 mm.

[0009] Furthermore, the mass ratio of the oil shale slag powder to sodium silicate nonahydrate is 1:1;

[0010] Furthermore, the stirring speed is 500 rpm; the stirring time is 60 min; and the ultrasonication time is 45 min.

[0011] Furthermore, the molar ratio of manganese in the manganese sulfate aqueous solution to silicon in the sodium silicate nonahydrate aqueous solution is 1~3:1~2.

[0012] Furthermore, the hydrothermal reaction temperature is 180°C, and the hydrothermal reaction time is 12 h.

[0013] Furthermore, the centrifugation speed is 6000 r·min. -1 The centrifugation time is 5 minutes.

[0014] Furthermore, the drying temperature is 70°C, the drying time is 24 h, the grinding time is 10 min, and the sieve aperture is 200 mesh.

[0015] A nanocomposite adsorbent for oil shale slag is prepared by the above method.

[0016] An application of the above-mentioned oil shale slag nanocomposite adsorbent is used for the adsorption of organic dyes.

[0017] Compared with existing technologies, this invention solves the problems of low controllability, poor stability, poor adsorption effect, poor repeatability, and short cycle life when applying oil shale slag to the field of adsorbents. Specifically, the beneficial effects are as follows:

[0018] 1. This invention uses oil shale slag as a carrier and prepares an oil shale slag nanocomposite adsorbent by constructing a nanoscale manganese silicate active phase in situ via hydrothermal methods. This forms a nanocomposite structure in which multi-level pores and high-density active sites coexist on the surface, significantly increasing the specific surface area, pore capacity, and number of surface functional groups. This structure significantly enhances the reactivity and removal capacity of the oil shale slag nanocomposite adsorbent for organic pollutants (the adsorption capacity for basic fuchsin and tetracycline reaches 372.74 mg / g and 232.61 mg / g, respectively, representing increases of 254% and 365% compared to pure OSC). Simultaneously, the loading of manganese silicate effectively suppresses the pH sensitivity issue inherent in the alkaline nature of oil shale slag. Furthermore, the adsorbent exhibits clear selectivity; its surface charge state changes synchronously with the ionic form of the target pollutant, enabling directional adsorption of dye molecules and effectively improving the stability of the adsorbent's performance. This fundamentally solves the problems of dye structural changes, adsorption behavior instability, and poor adsorption effects caused by the continuous release of alkali from OSC itself.

[0019] 2. The oil shale slag nanocomposite adsorbent provided by this invention exhibits excellent repeatability and cycle life. After five cycles of anhydrous ethanol adsorption-desorption, the surface active sites and pore structure of the adsorbent remain stable, with a removal rate of over 80% for basic fuchsin and over 76% for tetracycline. This is mainly due to the defect sites and surface hydroxyl functional groups formed in the adsorbent structure, which can interact with pollutant molecules through reversible coordination or hydrogen bonding during chemisorption, making the adsorption process both efficient and reversible. This achieves high adsorption capacity while maintaining the material's regenerative capacity. Furthermore, the uniform dispersion of the nanocomposite structure and the stable existence of the pore structure effectively prevent the loss or blockage of active sites during adsorption-desorption cycles, further extending the material's service life and reducing operating costs.

[0020] 3. The preparation process of this invention is simple, the raw materials are readily available, the energy consumption is low, the composition and performance stability of the product is improved between batches, which facilitates large-scale and continuous production, realizes the high-value utilization of bulk solid waste oil shale slag, effectively reduces the environmental risks that may be caused by stockpiling and strong alkali leaching, and has both high-efficiency pollutant removal capacity and solid waste resource utilization benefits, providing an economical, environmentally friendly and sustainable solution for water treatment and solid waste management. Attached Figure Description

[0021] Figure 1 The image shows the X-ray diffraction spectrum of the oil shale slag nanocomposite adsorbent; among which, Figure 1 (a) X-ray diffraction spectra of pure OSC and OSC-Ac; Figure 1 (b) is the X-ray diffraction spectrum of the oil shale slag nanocomposite adsorbent;

[0022] Figure 2 Fourier transform infrared spectrum of oil shale slag nanocomposite adsorbent;

[0023] Figure 3 The Raman spectrum of the oil shale slag nanocomposite adsorbent;

[0024] Figure 4 The image shows a scanning electron microscope image of the oil shale residue nanocomposite adsorbent; among which, Figure 4 (a) is a scanning electron microscope image of pure oil shale residue; Figure 4 (b~f) are scanning electron microscope images of the oil shale slag nanocomposite adsorbents prepared in Examples 1-5, respectively;

[0025] Figure 5 Energy dispersive X-ray spectra of pure oil shale residue and the oil shale residue nanocomposite adsorbent prepared in Example 3; wherein, Figure 5 (a) is the energy dispersive X-ray spectrum of pure oil shale residue; Figure 5(b) is the energy dispersive X-ray spectrum of the oil shale slag nanocomposite adsorbent prepared in Example 3;

[0026] Figure 6 The N2 adsorption-desorption isotherm curve of the oil shale slag nanocomposite adsorbent prepared in Example 3;

[0027] Figure 7 The pore size distribution curve of the oil shale slag nanocomposite adsorbent prepared in Example 3;

[0028] Figure 8 The curve shown is the kinetic fitting curve of the adsorption process of basic fuchsin by the oil shale residue nanocomposite adsorbent prepared in Example 3; wherein, Figure 8 (a) and (b) are the kinetic fitting curves of the pseudo-first-order kinetic model and the pseudo-second-order kinetic model, respectively, for the adsorption of basic fuchsin by the oil shale slag nanocomposite adsorbent prepared in Example 3. Figure 8 (c) is the intraparticle diffusion model fitting curve of the adsorption process of basic fuchsin by the oil shale slag nanocomposite adsorbent prepared in Example 3;

[0029] Figure 9 The curve shows the kinetic fitting of the tetracycline adsorption process by the oil shale slag nanocomposite adsorbent prepared in Example 3; wherein, Figure 9 (a) and (b) are the kinetic fitting curves of the pseudo-first-order kinetic model and the pseudo-second-order kinetic model, respectively, for the adsorption of tetracycline by the oil shale slag nanocomposite adsorbent prepared in Example 3. Figure 9 (c) is the fitting curve of the intraparticle diffusion model for the adsorption process of tetracycline by the oil shale slag nanocomposite adsorbent prepared in Example 3;

[0030] Figure 10 The figures show the fitting curves for the adsorption behavior of basic fuchsin by the oil shale residue nanocomposite adsorbent prepared in Example 3 using the Freundlich, Langmuir, and Temkin isotherm adsorption models; where, Figure 10 (a) is the fitting curve of Freundlich for the adsorption behavior of basic fuchsin by the oil shale slag nanocomposite adsorbent prepared in Example 3; Figure 10 (b) is the fitting curve of the Langmuir isotherm adsorption model for the adsorption behavior of basic fuchsin by the oil shale slag nanocomposite adsorbent prepared in Example 3; Figure 10 (c) is the fitting curve of the Temkin isotherm adsorption model for the adsorption behavior of basic fuchsin by the oil shale slag nanocomposite adsorbent prepared in Example 3;

[0031] Figure 11 The figures show fitting curves for the adsorption behavior of tetracycline by the oil shale slag nanocomposite adsorbent prepared in Example 3 using the Freundlich, Langmuir, and Temkin isotherm adsorption models; where... Figure 11 (a) is the fitting curve of Freundlich on the adsorption behavior of tetracycline by the oil shale slag nanocomposite adsorbent prepared in Example 3; Figure 11 (b) is the fitting curve of Langmuir isothermal adsorption model for the adsorption behavior of tetracycline by the oil shale slag nanocomposite adsorbent prepared in Example 3; Figure 11 (c) is the fitting curve of the Temkin isotherm adsorption model for the adsorption behavior of tetracycline by the oil shale slag nanocomposite adsorbent prepared in Example 3;

[0032] Figure 12 The graph shows the trend of the adsorption capacity of the oil shale residue nanocomposite adsorbent prepared in Example 3 for basic fuchsin and tetracycline as a function of pH; wherein, Figure 12 (a) is a graph showing the trend of the adsorption capacity of basic fuchsin by the oil shale slag nanocomposite adsorbent as a function of pH. Figure 12 (b) is a graph showing the trend of tetracycline adsorption capacity of oil shale slag nanocomposite adsorbent as a function of pH.

[0033] Figure 13 The graph shows the trend of the adsorption capacity of basic fuchsin and tetracycline by the oil shale slag nanocomposite adsorbent prepared in Example 3 as a function of CaCl2 concentration. Figure 13 (a) is a graph showing the trend of the adsorption capacity of basic fuchsin by the oil shale slag nanocomposite adsorbent prepared in Example 3 as a function of CaCl2 concentration; Figure 13 (b) is a graph showing the trend of tetracycline adsorption capacity of the oil shale slag nanocomposite adsorbent prepared in Example 3 as a function of CaCl2 concentration;

[0034] Figure 14 The graph shows the cyclic adsorption-desorption trend of basic fuchsin and tetracycline by the oil shale slag nanocomposite adsorbent prepared in Example 3; where, Figure 14 (a) is a graph showing the cyclic adsorption-desorption trend of basic fuchsin by the oil shale slag nanocomposite adsorbent prepared in Example 3; Figure 14 (b) is a graph showing the cyclic adsorption-desorption trend of tetracycline by the oil shale slag nanocomposite adsorbent prepared in Example 3. Detailed Implementation

[0035] To make the technical solutions of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. It should be noted that the following embodiments are only used to better understand the technical solutions of the present invention and should not be construed as limiting the present invention.

[0036] Example 1.

[0037] Dissolve 0.015 mol sodium silicate nonahydrate in 50 mL of deionized water to obtain a 0.30 mol / L sodium silicate nonahydrate aqueous solution; grind oil shale slag in a ball mill at 200 r·min -1 The oil shale slag powder was obtained by ball milling at a certain speed for 40 min to reduce its particle size. 2 g of the oil shale slag powder was dispersed in sodium silicate nonahydrate aqueous solution and stirred for 60 min. The mixture was then ultrasonicated 5 times, 10 min each time, to ensure thorough mixing and obtain suspension 1. 0.005 mol of manganese sulfate monohydrate was dissolved in 30 mL of deionized water. The manganese sulfate aqueous solution was then added dropwise to suspension 1 using a dropper, and the mixture was stirred to obtain a homogeneous suspension 2. The molar ratio of manganese in the manganese sulfate aqueous solution to silicon in the sodium silicate nonahydrate aqueous solution was 3:1. Suspension 2 was transferred to a polytetrafluoroethylene reactor and sealed for hydrothermal reaction at 180℃ for 12 h. After the reactor cooled naturally to room temperature, the product was diluted with deionized water at 6000 r·min⁻¹. -1 Centrifuge at a certain speed for 5 min, repeat centrifugation until pH is neutral; dry the product in an oven at 70℃ for 24 h to constant weight, grind the product, and sieve it through a sieve with a pore size of 200 to obtain the oil shale slag nanocomposite adsorbent, denoted as Mn@OSC-1.

[0038] Example 2.

[0039] The difference between this embodiment and Example 1 is that 0.015 mol sodium silicate nonahydrate was dissolved in 50 mL of deionized water to obtain a 0.30 mol / L sodium silicate nonahydrate aqueous solution; 0.075 mol manganese sulfate monohydrate was weighed and dissolved in 30 mL of deionized water, and then the manganese sulfate aqueous solution was added dropwise to suspension 1 using a dropper, and stirred to obtain a uniform suspension 2. The molar ratio of manganese in the manganese sulfate aqueous solution to silicon in the sodium silicate nonahydrate aqueous solution was 2:1. The remaining preparation steps and conditions were the same as in Example 1, and the oil shale slag nanocomposite adsorbent was obtained, denoted as Mn@OSC-2.

[0040] Example 3.

[0041] The difference between this embodiment and Example 1 is that 0.015 mol sodium silicate nonahydrate was dissolved in 50 mL of deionized water to obtain a 0.30 mol / L sodium silicate nonahydrate aqueous solution; 0.01 mol manganese sulfate monohydrate was weighed and dissolved in 30 mL of deionized water, and then the manganese sulfate aqueous solution was added dropwise to suspension 1 using a dropper, and stirred to obtain a uniform suspension 2. The molar ratio of manganese in the manganese sulfate aqueous solution to silicon in the sodium silicate nonahydrate aqueous solution was 1.5:1. The remaining preparation steps and conditions were the same as in Example 1, and the oil shale slag nanocomposite adsorbent was obtained, denoted as Mn@OSC-3.

[0042] Example 4.

[0043] The difference between this embodiment and Example 1 is that 0.015 mol sodium silicate nonahydrate was dissolved in 50 mL of deionized water to obtain a 0.30 mol / L sodium silicate nonahydrate aqueous solution; 0.015 mol manganese sulfate monohydrate was weighed and dissolved in 30 mL of deionized water, and then the manganese sulfate aqueous solution was added dropwise to suspension 1 using a dropper, and stirred to obtain a uniform suspension 2. The molar ratio of manganese in the manganese sulfate aqueous solution to silicon in the sodium silicate nonahydrate aqueous solution was 1:1. The remaining preparation steps and conditions were the same as in Example 1, and the oil shale slag nanocomposite adsorbent was obtained, denoted as Mn@OSC-4.

[0044] Example 5.

[0045] The difference between this embodiment and Example 1 is that 0.015 mol sodium silicate nonahydrate was dissolved in 50 mL of deionized water to obtain a 0.30 mol / L sodium silicate nonahydrate aqueous solution; 0.03 mol manganese sulfate monohydrate was weighed and dissolved in 30 mL of deionized water, and then the manganese sulfate aqueous solution was added dropwise to suspension 1 using a dropper, and stirred to obtain a uniform suspension 2. The molar ratio of manganese in the manganese sulfate aqueous solution to silicon in the sodium silicate nonahydrate aqueous solution was 1:2. The remaining preparation steps and conditions were the same as in Example 1, and the oil shale slag nanocomposite adsorbent was obtained, denoted as Mn@OSC-5.

[0046] X-ray diffraction spectroscopy was performed on the oil shale slag nanocomposite adsorbents Mn@OSC-1~5 prepared in Examples 1-5, as shown in the results. Figure 1 (a) shows the X-ray diffraction (XRD) spectra of pure OSC and OSC-Ac, where OSC-Ac is OSC soaked in acetic acid to remove impurities and some metal oxides. As can be seen from the figure, the OSC and OSC-Ac frameworks before loading manganese silicate exhibit typical diffraction characteristic peaks of aluminosilicate minerals such as quartz, albite, and a small amount of zeolite; Figure 1 (b) shows the XRD patterns of Mn@OSC-1~5. As can be seen from the figure, the diffraction peak distribution of the oil shale slag nanocomposite adsorbent exhibits more complex characteristics, especially Mn@OSC-3, which shows the characteristic peak of analcime, indicating that OSC can form analcime crystalline phase under hot alkaline conditions. Furthermore, amorphous broad peaks appear at 2θ≈33° and 57°. These amorphous dispersed peaks indicate the deposition and growth of manganese silicate on the OSC surface, suggesting that the loading process introduces a new amorphous phase. Under hydrothermal alkaline conditions, manganese ions react with silicate ions to generate amorphous manganese silicate. It can be seen that the introduction of manganese silicate not only changes the local crystal structure of OSC, but also enables manganese silicate to be successfully loaded on the OSC surface, forming a multiphase composite structure, increasing adsorption sites, and laying the foundation for improving the adsorption of organic pollutants.

[0047] Infrared spectroscopy was performed on the oil shale slag nanocomposite adsorbents Mn@OSC-1~5 prepared in Examples 1-5, such as... Figure 2 The image shows the Fourier transform infrared (FTIR) spectra of Mn@OSC-1~5. As can be seen from the image, the original OSCs exhibit typical silicon-oxygen tetrahedral stretching vibration peaks (at 1040 cm⁻¹). -1 The manganese silicate exhibits typical characteristics of aluminosilicate minerals, including Si-O-Al bending vibration peaks and surface hydroxyl absorption peaks. When manganese silicate is loaded with oil shale slag, a new Mn-OH peak appears in the nanocomposite adsorbent, especially in Mn@OSC-3 where the Mn-OH absorption peak intensity is significantly enhanced; simultaneously, at 800–900 cm⁻¹... -1 New silicon-oxygen bond distortion peaks also appeared in the vibration region, which is related to the local structural rearrangement of the silicon-oxygen tetrahedral structure after manganese loading. This process also proves that the accompanying hydroxyl groups on the surface are involved in the bonding, proving that manganese silicate was successfully loaded on the OSC surface.

[0048] like Figure 3 The figures show the Raman spectra of the oil shale slag nanocomposite adsorbents Mn@OSC-1~5 prepared in Examples 1-5. It can be seen from the figures that the Ig of pure OSC... D / I G With an I content of only 0.73, it exhibits a relatively complete and ordered carbon structure; while Mn@OSC-3 has an I content of only 0.73. D / I G The value was as high as 2.78, significantly higher than other samples, indicating that the loading of manganese silicate in the Mn@OSC-3 sample increased defects and the structure was more disordered. This proves that the incorporation of an appropriate amount of manganese ions may lead to changes in local structure or the generation of defects, further promoting the formation of disordered structures in Mn@OSC-3. The increase in defects means that the nanocomposite adsorbent may have a higher density of active sites, especially when adsorbing organic dyes, metal ions or antibiotic pollutants with dipole moments. The defective surface can enhance the interfacial binding ability and improve the efficiency of electronic interaction, hydrogen bonding effect or electrostatic adsorption.

[0049] like Figure 4 The image shown is a scanning electron microscope (SEM) image of the oil shale slag nanocomposite adsorbent Mn@OSC-1~5 prepared in Examples 1-5. Figure 4 (a) is a SEM image of pure OSC. As can be seen from the image, the surface morphology of pure OSC is relatively compact and consists of irregular flakes. There are clusters of aluminosilicate particles attached to the surface, along with a small amount of macroporous structure after sintering. Figure 4(b~f) are SEM images of Mn@OSC-1~5, respectively. The images show that after loading manganese silicate, the Mn@OSC samples all exhibited increased porosity, disrupting the dense, lamellar structure. In particular, Mn@OSC-3 exhibited a uniformly dispersed, small, and highly porous pore structure, with uniformly attached manganese silicate nanoparticles. The presence of these particles indicates successful loading of manganese silicate onto the OSC surface.

[0050] like Figure 5 The image shown is the energy dispersive X-ray spectroscopy (EDS) spectrum of the oil shale residue nanocomposite adsorbent Mn@OSC-3 prepared in Example 3. Figure 5 (a) is the EDS diagram of OSC. It can be seen from the diagram that OSC is mainly composed of elements such as O, Si, C, Al, Fe, and Ca. Figure 5 (b) is the EDS plot of Mn@OSC-3. As can be seen from the figure, Mn@OSC-3 is mainly composed of elements such as O, Si, C, Mn, Na, and Al, with Mn accounting for 11% by mass and 0.4% by atomic percentage. This also indicates that manganese silicate was successfully loaded onto OSC.

[0051] like Figure 6 The figure shows the N2 adsorption-desorption isotherm curve of the oil shale slag nanocomposite adsorbent Mn@OSC-3 prepared in Example 3. As can be seen from the figure, the isotherm curve of Mn@OSC-3 generally exhibits typical Type IV characteristics, accompanied by obvious hysteresis loop. Compared with pure OSC, the adsorption capacity of Mn@OSC-3 is significantly increased throughout the entire relative pressure range, especially in the high relative pressure range where the adsorption capacity rises rapidly. This indicates that the number of pores is significantly increased and the pore connectivity is better, which is conducive to the entry and diffusion of adsorbate.

[0052] like Figure 7 The figure shows the pore size distribution curve of the oil shale slag nanocomposite adsorbent Mn@OSC-3 prepared in Example 3. Table 1 shows the comparison results of the pore structure parameters of pure OSC and Mn@OSC-3. Figure 7 As can be seen from Table 1, the specific surface area of ​​pure OSC is only 7.1143 m². 2 / g, its pore structure mainly consists of large pores and irregular fractures formed after the combustion of oil shale, with limited overall porosity. Meanwhile, the specific surface area of ​​Mn@OSC-3 jumps to 361.5920 m². 2 / g, an increase of over 50 times, resulting in a significant improvement in specific surface area. Simultaneously, the total pore volume (V-total) of Mn@OSC-3 reached 0.399 cm³. 3 / g, while pure OSC is only 0.03cm 3 / g, the difference between the two is more than an order of magnitude, indicating that a large number of new mesoporous structures were successfully generated during the loading process. Combined with Figure 4 SEM morphology analysis also verified that the uniformly sized and well-dispersed nano-manganese silicate particles formed on the surface of Mn@OSC-3 constructed a large number of new mesoporous structures at the interface. The gaps between these nanoparticles and their bonding interface with the OSC framework together determine the highly open microporous and mesoporous system of Mn@OSC-3, thus forming an adsorption and diffusion channel that is far superior to that of the original material.

[0053] Table 1

[0054]

[0055] To prepare standard solutions of basic fuchsin (BF) and tetracycline (TC), weigh 0.4 g of basic fuchsin and 0.4 g of tetracycline powder into a beaker, add distilled water, and stir continuously with a glass rod until the dyes are completely dissolved. Transfer the solution to a 1 L volumetric flask, add distilled water to make up to the final volume, and shake well to obtain a 400 mg / L dye standard solution. Dilute the solution according to its concentration when determining the standard curve. For the adsorption experiment, a standard batch method was used. Weigh an appropriate amount of Mn@OSC-3 adsorbent into an Erlenmeyer flask, then add the basic fuchsin and tetracycline solutions using a 25 mL pipette. Shake the mixture at a constant temperature to ensure thorough mixing and reaction. Pour the mixture into a 30 mL centrifuge tube and centrifuge at 5000 r·min⁻¹. -1 Centrifuge at a certain speed for 10 min, take the supernatant and measure the absorbance in a UV-Vis spectrophotometer. By plotting the pollutant standard curve, fit the equation to calculate the adsorption amount (mg / g) and removal rate R (%) of the adsorbent for the dye.

[0056] At 25℃ and an initial BF concentration of 400 mg / L, 25 mg of Mn@OSC-3 was added, such as... Figure 8 Figures (a) and (b) show the kinetic fitting curves of the pseudo-first-order and pseudo-second-order kinetic models for the adsorption of basic fuchsin (BF) by Mn@OSC-3, respectively. As can be seen from the figures, Mn@OSC-3 exhibits significant rapid adsorption characteristics in the initial adsorption stage and reaches adsorption equilibrium in a relatively short time, with its equilibrium adsorption capacity being significantly higher than that of OSC. The goodness of fit (R0) of the pseudo-second-order kinetic model to the BF adsorption process of Mn@OSC-3 is shown in Figure (a). 2 =0.996), significantly outperforming the pseudo-first-order model (R² = 0.996). 2 =0.951), indicating that the process is mainly controlled by chemisorption, and the adsorption rate is dominated by the interfacial reaction between the active sites on the adsorbent surface and the dye molecules. Figure 8(c) Fitting curves of intraparticle diffusion model for the adsorption process of basic fuchsin (BF) by Mn@OSC-3 and OSC. As can be seen from the figure, the adsorption process is not controlled by a single diffusion mechanism, but is jointly participated by surface adsorption and intrapore diffusion. The higher diffusion slope and adsorption capacity of Mn@OSC-3 indicate that its pore structure and surface chemical properties are more conducive to the rapid mass transfer and stable fixation of BF molecules.

[0057] At 25°C and an initial tetracycline (TC) concentration of 400 mg / L, 25 mg of Mn@OSC-3 was added, as follows: Figure 9 Figures (a) and (b) show the kinetic fitting curves of the pseudo-first-order and pseudo-second-order kinetic models for the adsorption of tetracycline (TC) by Mn@OSC-3, respectively. As can be seen from the figures, Mn@OSC-3 also exhibits a significant rapid adsorption characteristic for TC. The adsorption amount increases rapidly in the initial stage of adsorption, then gradually stabilizes and reaches adsorption equilibrium in a short time. Its equilibrium adsorption amount is significantly higher than that of OSC, indicating that the manganese silicate-modified material has a better adsorption capacity for antibiotic pollutants. The goodness of fit (R0) of the pseudo-second-order kinetic model to the TC adsorption process of Mn@OSC-3 is shown in the figure. 2 =0.991) is significantly better than the pseudo-first-order dynamic model (R 2 =0.924), indicating that the adsorption process of TC on the Mn@OSC-3 surface is mainly controlled by the chemisorption mechanism, and the adsorption rate is dominated by the interfacial reaction between the active sites on the adsorbent surface and TC molecules. Figure 9 (c) shows the intraparticle diffusion model fitting curves of the adsorption process of tetracycline (TC) by Mn@OSC-3 and OSC. It can be seen from the figure that the adsorption process is not controlled by a single diffusion step, but rather goes through a multi-stage process of rapid adsorption on the outer surface and subsequent intrapore diffusion. The larger diffusion slope and higher adsorption capacity of Mn@OSC-3 further indicate that its optimized pore structure and enhanced surface chemical activity effectively promote the mass transfer and stable adsorption of TC molecules.

[0058] At 25℃, using 25 mL of basic fuchsin (BF) solutions of different initial concentrations as the adsorption system, 25 mg of Mn@OSC-3 was added and the adsorption reaction was carried out for 180 min. Figure 10Figures (a)–(c) show the fitting curves of the Freundlich, Langmuir, and Temkin isotherm adsorption models for the BF adsorption behavior of Mn@OSC-3 and OSC, respectively. As can be seen from the figures, with increasing initial BF concentration, the equilibrium adsorption capacity of Mn@OSC-3 continuously increases and gradually stabilizes, with its overall adsorption capacity significantly higher than that of OSC. This indicates that manganese silicate modification significantly enhances the interfacial binding ability of the material to dye molecules. The Langmuir isotherm model's goodness of fit (R0) to the BF adsorption process of Mn@OSC-3 is shown in the figures. 2 =0.997) is significantly better than the Freundlich model (R² = 0.997). 2 =0.848) and Temkin model (R 2 =0.947), indicating that the adsorption of BF on the Mn@OSC-3 surface is more consistent with the characteristics of monolayer adsorption. The adsorption process mainly occurs on a limited and uniform number of active sites, and is dominated by chemisorption. In contrast, OSC has a lower correlation coefficient in all models, further confirming the significant advantages of Mn@OSC-3 in terms of the number of surface active sites, adsorption energy distribution, and interfacial reactivity.

[0059] Under the same temperature and addition conditions, using 25 mL of tetracycline (TC) solutions with different initial concentrations as the adsorption system, and a reaction time of 180 min, as follows: Figure 11 Figures (a) to (c) show the fitting curves of the Freundlich, Langmuir, and Temkin isotherm adsorption models for the adsorption of TC by Mn@OSC-3 and OSC, respectively. As can be seen from the figures, the equilibrium adsorption capacity of Mn@OSC-3 for TC gradually increases with increasing initial concentration, and tends to saturate in the high concentration range. Its adsorption capacity is consistently significantly higher than that of OSC, demonstrating the good adaptability of this material to antibiotic pollutants. The isotherm model fitting results show that the Langmuir model has a high degree of fit (R0) to the TC adsorption process of Mn@OSC-3. 2 =0.991) is better than the Freundlich model (R² = 0.991). 2 =0.901) and Temkin model (R 2 =0.982), indicating that the adsorption of TC on the Mn@OSC-3 surface is also a monolayer adsorption process, with a relatively uniform distribution of adsorption sites, and the adsorption process is mainly based on chemisorption mechanism. Therefore, the composite adsorbent provided by this invention exhibits stable and predictable monolayer adsorption characteristics in different organic pollutant systems, providing a reliable kinetic basis for its application in practical water treatment.

[0060] The adsorption performance of Mn@OSC-3 for pollutants is significantly affected by the pH value of the solution, such as Figure 12(a) is a graph showing the trend of BF adsorption capacity of Mn@OSC-3 with pH. It can be seen from the graph that the adsorption capacity of BF by Mn@OSC-3 generally increases with increasing pH, indicating that the surface charge state of the material is more conducive to the adsorption of BF molecules under alkaline conditions. Figure 12 (b) The adsorption capacity of Mn@OSC-3 for TC changes with pH. The graph shows that the adsorption capacity for TC decreases significantly with increasing pH, indicating that the electrostatic repulsion between the Mn@OSC-3 surface and TC increases with increasing alkalinity, thus inhibiting the adsorption process. Therefore, the composite adsorbent provided by this invention exhibits a significant pH response, enabling pollutants to undergo directional adsorption under stable and controllable acid-base conditions. This fundamentally solves the problem of dye structural changes and adsorption behavior instability caused by the alkalinity of OSC itself.

[0061] like Figure 13 (a) and (b) are graphs showing the adsorption capacity of Mn@OSC-3 for BF and TC as a function of CaCl2 concentration, respectively, prepared in Example 3. The graphs show that as the CaCl2 concentration increases, the adsorption capacity of Mn@OSC-3 for BF increases, while the adsorption capacity for TC decreases significantly. This indicates that as the CaCl2 concentration gradually increases, the additional electrolyte ions appearing in the system compete with the pollutants and the active sites on the adsorbent surface, altering the interfacial charge distribution and resulting in differentiated adsorption responses. Therefore, the composite adsorbent provided by this invention not only achieves targeted adsorption of the target pollutants but also exhibits controllable interfacial response characteristics to changes in electrolyte ion concentration, ensuring stable selective adsorption capacity under complex hydrochemical conditions.

[0062] like Figure 14 (a) and (b) are the cyclic adsorption-desorption trend diagrams of BF and TC prepared by Mn@OSC-3 in Example 3, respectively. After five cycles of anhydrous ethanol adsorption-desorption, the removal rate of basic fuchsin by Mn@OSC-3 is still above 80%, and the removal efficiency of tetracycline is still above 76%. This indicates that the material structure was not significantly damaged during solvent desorption, and its surface active sites have high stability and reusability required for practical engineering applications, laying the foundation for its continuous application in wastewater treatment.

[0063] In summary, this invention uses oil shale slag as a carrier and prepares an oil shale slag nanocomposite adsorbent by constructing a nano-manganese silicate active phase in situ via hydrothermal methods. This results in a nanocomposite structure with multi-level pores and high-density active sites on the surface, significantly increasing the specific surface area, pore capacity, and number of surface functional groups. This structure significantly enhances the reactivity and removal capacity of the oil shale slag nanocomposite adsorbent for organic pollutants. Simultaneously, the adsorbent can achieve directional adsorption of dye molecules, effectively improving the stability of the adsorbent's performance. It exhibits excellent repeatability and cycle life, realizing the high-value utilization of bulk solid waste oil shale slag. This invention combines highly efficient pollutant removal with solid waste resource utilization benefits, providing an economical, environmentally friendly, and sustainable solution for water treatment and solid waste management.

[0064] The above description of the embodiments is only for the purpose of helping to understand the method and core ideas of the present invention. It should be noted that those skilled in the art can make several improvements and modifications to the present invention without departing from the principles of the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

[0065] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A nanocomposite adsorbent for oil shale slag, characterized in that, The oil shale slag powder was prepared by dispersing it in an aqueous solution of sodium silicate nonahydrate, stirring and sonicating to obtain suspension 1; an aqueous solution of manganese sulfate was added to suspension 1 to obtain suspension 2; suspension 2 was subjected to a hydrothermal reaction, and the reaction product was centrifuged until the pH was neutral; the product was dried, ground, and sieved to obtain the oil shale slag nanocomposite adsorbent. The mass ratio of the oil shale residue powder to sodium silicate nonahydrate is 1:1; The molar ratio of manganese in the manganese sulfate aqueous solution to silicon in the sodium silicate nonahydrate aqueous solution is 1~3:1~2.

2. The oil shale slag nanocomposite adsorbent according to claim 1, characterized in that, The oil shale residue powder is prepared by mixing oil shale residue at 200 r·min -1 The oil shale slag powder was obtained by ball milling at a certain speed for 40 min; the particle size of the powder was 0.075 mm.

3. The oil shale slag nanocomposite adsorbent according to claim 1, characterized in that, The stirring speed was 500 rpm; the stirring time was 60 min; and the ultrasonication time was 45 min.

4. The oil shale slag nanocomposite adsorbent according to claim 1, characterized in that, The hydrothermal reaction was carried out at a temperature of 180°C for 12 hours.

5. The oil shale slag nanocomposite adsorbent according to claim 1, characterized in that, The centrifuge speed is 6000 r·min -1 The centrifugation time is 5 minutes.

6. The oil shale slag nanocomposite adsorbent according to claim 1, characterized in that, The drying temperature is 70°C, and the drying time is 24 hours; the sieve aperture is 200 mesh.

7. The application of an oil shale slag nanocomposite adsorbent as described in any one of claims 1-6, characterized in that, It is used for adsorbing organic dyes.

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